Auto-darkening welding lenses are able to adjust their darkening levels according to the welding arc, completely preventing electro-ophthalmia, an occupational disease among welders. So the welder can work with both his hands, auxiliary procedures for welding are cut, welding quality and efficiency are improved, and no-load power consumption of the welding machine is reduced. It can be seen that the auto-darkening welding lens is going to be the next leading welding protection product. However, the auto-darkening welding lens includes infrared-blocking and ultraviolet-blocking filters and two liquid crystal plates, resulting low light transmittance when not exposed to the welding arc; hence, the welder may have a hard time locating the welding point under low indoor lighting conditions or when the equipment is backlit, which may cause poor welds.